1. Field of the Invention
The present embodiments relate generally to a pretensioner system for a seatbelt. More specifically, the present embodiments relate to a pyrotechnic lap pretensioner.
2. Description of Related Art
The use of seatbelt pretensioners for pretensioning a seatbelt in the event of a collision is common in the art. Pretensioners can be used, generally, to pretension a seatbelt during a collision, which will cause the seatbelt to become tighter on the occupant wearing the seatbelt. Tightening the seatbelt in the event of a collision can limit the amount that the occupant will travel forward during a crash. Pretensioners are generally activated by sensors in the vehicle that determine that a collision has occurred.
One type of pretensioners is known as a linear pretensioner, and involves the use of a piston that travels linearly, thereby linearly pulling on the lap belt in a single direction. The piston can be attached to an end of the seatbelt and, once activated, the piston will travel in a direction, pulling the seatbelt in the same direction. However, these devices are limited in the amount that the seatbelt can be pulled by the length of the piston. Space constraints with in the vehicle can limit the size and length of the piston, thereby limiting the length that the belt can be pulled.
Another type of pretensioner is in the form or a rotary pretensioner. A rotary pretensioner includes a rotatable spool or pinion having a plurality of teeth extending radially outward. The rotary pretension also includes a plurality of ball shaped weights that are housed in a tube. The tube is connected to a gas generator. In the event of a collision, the gas generator can be activated to fire the weights along a guide path toward the spool. The weights will approach the spool in a generally tangential manner, making contact with the teeth and causing the spool to rotate about a spindle. The spindle is connected to the seatbelt webbing, causing the seatbelt to become wound, thereby shortening the length of the belt and pretensioning the belt. However, this type of pretensioner requires numerous moving ball weights through a path, and the amount of winding of the spool depends on the number of ball weights. To increase the amount of available pretensioning, the number of ball weights must be increased. The vehicle cabin and seatbelt mechanisms have a limited amount of available area for installation, which conflicts the space desired for the pretensioner.